Number of Adult Culicoides Brevitarsis Kieffer (Diptera: Ceratopogonidae) Emerging From Bovine Dung Exposed Under Different Conditions in the Field.

Abstract

Numbers were recorded of adult C. brevitarsis emerging from standard samples from variously treated dung pats. Adult emergence was a more efficient technique than the extraction of immatures. Emergence increased linearly by from three to four ovipositions per pat per day over the first 7 days of exposure of pats in the field. Oviposition occurred throughout the diel, maximum 1400-1800 h and minimum 0000-0700 h. Emergence began 11 days after pats were exposed and was completed by day 24. From days 12 to 24 numbers emerging halved every 1.7 days. Eggs were deposited all over the upper surface of pats with greatest density at the centre. Number emerging per unit area was independent of pat size. Adults emerged from pats of varying shape in plan view but few from pats sunk flush with the ground, surrounded by a sleeve, or subjected to heavy rain within 24 h of deposition. It is suggested that emergence rates reflect oviposition rates, and it is concluded that C. brevitarsis orients visually to dung, probably while flying above it. The rounded sides of the pats may be very important.

Effect of Temperature Regimes on the Development, Survival and Emergence of Culicoides brevitarsis Kieffer (Diptera: Ceratopogonidae) in Bovine Dung

“…Development Two days of oviposition was a compromise between minimising time in the field and ensuring sufficient numbers of C. brevitarsis would be available for testing (Bishop et al 1996). This induced relatively discrete populations in the dung and would have excluded individuals from eggs that can be laid for several more days (Campbell and Kettle 1976). C. brevitarsis would therefore be expected to emerge over a longer period in the field than that described here.…”

Positions of Juvenile Stages of Culicoides brevitarsis Kieffer (Diptera: Ceratopogonidae) and of Four Other Flies in Bovine Dung

“…Behaviourally, A . niveipennis and L. rnirabilis oviposited in the upper half of the dung as does C. brevitarsis (Campbell and Kettle 1976). Psychoda sp.…”

“…niveipennis was biased by its distribution (oviposition) at day 1. The same may be true of C. brevitarsis where greatest density of eggs has been found at the centre of the pat (Campbell and Kettle 1976). Taking cores of dung at random to standardise sample size and to include all juvenile stages would be the method most applicable to these two species after eggs hatch.…”

“…Exposure was timed to avoid interference from wind and rain. A maximum 2-d oviposition period was a compromise between minimum time in the field and expectations of numbers of C. brevitarsis derived previously and from the literature (Bishop and McKenzie 1994;Campbell and Kettle 1976). After 2 d , the 18 remaining pats were picked up at ground level with a shovel, placed on wooden boards and returned to a glasshouse where further studies were carried out in late March 1995 with temperature maintained at 25 f 3°C and with ambient humidity and natural light.…”

“…Allingham 1991; Campbell 1974; Campbell and Kettle 1976). While much valuable information has been derived, some of these studies were limited by deficiencies in their methodology and the need to remove larvae and pupae from dung for testing.…”